With conventional fuel injectors for injection systems of internal combustion engines, the fuel injection is typically controlled by means of a valve needle which is disposed so as to form a movable seal within a guide in a valve body of an injection valve. At its tip the valve needle has a valve needle seat which, together with a valve body seat of the valve body, opens or closes at least one nozzle orifice to the combustion chamber of the internal combustion engine. The at least one nozzle orifice is typically disposed in the area of the valve body seat.
The purpose of the injection nozzle is to supply the combustion chamber of the internal combustion engine with fuel in a selective and metered manner. The type of fuel conditioning is significantly influenced by the injection nozzle and the progression of the injection operation. This, in turn, can have a major influence of the combustion of the internal combustion engine. With the injection nozzle closed, when the cone of the nozzle needle sits against the conical sealing surface of the nozzle body, the nozzle needle is centered in the nozzle body as a result of this seating contact. However, when the nozzle needle lifts off from the conical sealing surface, the nozzle needle, which then projects freely into the tip of the nozzle body, tends to deviate from the precisely centered position. The consequence of this is that the encircling injection orifices are not released uniformly, which can lead in turn to an asymmetrical jet formation which may have a negative impact on the combustion cycle and consequently also on the emission values.
In order to ensure a uniform jet pattern of the various injection orifices, it is proposed in DE 198 43 616 A1 that the nozzle body of the injection nozzle be provided with a cylinder-shaped recess in the interior of the tip in the area of the injection orifices. By means of the groove the flow is able to bypass the needle seat geometry with minimum flow losses. On the other hand, the introduction of the groove results in an additional so-called damage volume, i.e. a volume between nozzle body and nozzle needle which has a detrimental impact on the engine function with regard to exhaust gas emissions.